The present invention relates to an electrophotographic recording material comprising a metallic base, a layer of selenium containing tellurium arranged thereon, and a further layer of selenium arranged on the first layer.
From German Patent DE-AS No. 1,932,105 there is already known an electrophotographic recording material in which, on a metallic base, there is arranged a layer of selenium and on this a layer of selenium-tellurium. From this prior art there is further known an electrophotographic recording material in which on a metallic base there is arranged a layer of selenium-tellurium on which, in turn, there is arranged a layer of selenium, and with an insulating layer being arranged on this layer of selenium. In this case there may exist a continuous transition from the layer of selenium-tellurium to the layer of selenium.
Moreover, from German Patent DE-AS No. 2,305,407 there is known an electrophotographic recording material in which on a metallic base there is arranged a layer of selenium having a thickness ranging between 5 and 50 .mu.m (micrometer), on which layer there is arranged a layer of selenium with an addition of lead, with this layer of selenium containing lead being topped by a layer of selenium containing arsenide, having a thickness ranging between 1 and 50 .mu.m.
Further, from the report of the 1981 Meeting on Electrophotography in Venice, on page 125 there is described a sequence of layers in which on a base there is arranged an amorphous layer of selenium having a thickness of 60 .mu.m, on which, in turn, there is arranged a layer of selenium-tellurium having a thickness of 0.3 .mu.m, with this layer of selenium-tellurium being topped by a very thin protective layer of arsenic-selenium.
Finally, from German Patent DE-AS No. 1,277,016 it is known to arrange on an insulating base a layer of selenium-tellurium having a thickness of 0.1 .mu.m, and on this a layer of an insulating photoconductor, such as a layer of selenium having a thickness of 50 .mu.m. Relative thereto, the thickness of the thin layer of selenium-tellurium may not exceed 0.2 .mu.m.
As can be seen from the aforementioned prior art, the electrophotographic properties of a layer structure including a metallic base, a layer of selenium-tellurium having a thickness of 25 .mu.m, a layer of selenium having a thickness of 1 .mu.m, and a protective layer of polycarbonate, is not satisfactory. Owing to the protective layer provided for in the conventional arrangement, comprising a pure insulator, the electrophotographic properties of the recording material are deteriorated.
An improvement can of course be achieved by using as the protective layer a layer of selenium-arsenic, as is described in the report of the 1981 meeting in Venice. Such a photosensitive protective layer provided a substantial improvement of the charge fatigue. Such a layer structure, however, has a poor residual potential behaviour.